The present invention relates generally to hierarchical feedback control of pulsed laser deposition (PLD).
PLD is a new deposition method that utilizes high energy pulses of laser light in a vacuum to liberate material for deposition onto a surface. Many new thin films are complex in chemical and physical composition. PLD is a means in which complex molecular structures can be deposited on surfaces. PLD is unique in that high energies are used to motivate the material that is deposited. One of the difficulties with PLD is that the interaction of laser light pulses and material is poorly understood, when laser light in the UV spectrum is used. Unfortunately, UV laser light also is higher in energy, thus capable of providing higher deposition energy. Materials deposited by PLD range from tribological materials to superconductors. PLD also has application as an analysis tool, such as electrophoresis. Unfortunately, PLD has yet to be utilized as an industrial deposition process, due to implementation complexities and uncertainty of theoretical understanding. Overcoming these barriers by feedback control enables PLD to produce superior materials. Development of a control design methodology specific to PLD is necessary so reduced uncertainty can be realized, ultimately improving thin film quality.
The following technical paper publications are of interest with respect to the present invention.
S. J. P. Laube and E. F. Stark, "Feedback Control of Pulsed Laser Deposition Processes", AIP Conf. Proceedings 288, Laser Ablation: Mechanisms and Applications-II, Second International Conference, Knoxville, Tenn., April 1993. pp.242-247.
E. F. Stark and S. J. P. Laube, "Self Directed Control of Pulsed Laser Deposition", ASM Journal of Materials Engineering and Performance, Vol. 2, No. 5, October, 1993, pp.721-725 [cited as JMEPEG (1993)2:721-726], ASM International.RTM., Matertials Park, Ohio 44073-0002.
S. J. P. Laube and E. F. Stark, "Artificial Intelligence in Process Control of Pulsed Laser Deposition", AIRTC'94 Symposium on Artificial Intelligence in Real Time Control (Preprints), Valencia, 3-5 October 1994.
The above three papers authored by applicants are closely related to the invention.
Other papers of interest include:
J. Cheung, J. Horowitz, "Pulsed Laser Deposition History and Laser-Target Interactions" MRS Bulletin, vol. 17, No. 2 (February 1992), pp 30-36.
R. K. Singh and J. Narayan, "Pulsed-Laser Evaporation Technique for Deposition of Thin Films: Physics and Theoretical Model", Physical Review B, The American Physical Society, Vol. 41, No. 13, May 1990.
P. S. P. Wei, R. B. Hall, and W. E. Maher, "Study of Laser-Supported detonation Waves by Time-Resolved Spectroscopy", The Journal of Chemical Physics, Vol. 59, No. 7, 1 October 1973, pp. 3692-3700.
D. B. Geohegan, "Physics and Diagnostics of Laser Ablation Plume Propagation for High-T.sub.c Superconductor Film Growth", Solid State Division, Oak Ridge National Laboratory, P.O. Box 2008, Oak Ridge, Tenn. 37831-6056, submitted for the International Conference on Metallurgical Coatings and Thin Films, ICMCTF-92, San Diego, Calif., Apr. 6-10, 1992.
D. B. Geohegan, "Effects of Ambient Background Gases on YBCO Plume Propagation Under Film Growth Conditions: Spectroscopic, Ion Probe, and Fast Photographic Studies", Solid State Division, Oak Ridge National Laboratory, P.O. Box 2008, Oak Ridge, Tenn. 37831-6056, submitted for the E-MRS Summer School on Laser Ablation of Electronic Materials: Basic Mechanisms and Applications, Carcans-Maubuisson, France, September, 1991.
D. B. Chrisey and A. Inam, "Pulsed Laser Deposition of High T.sub.c Superconducting Thin Films for Electronic Device Applications", MRS Bulletin, February 1992.
S. R. Foltyn, R. E. Muenchausen, R. C. Estler, E. Peterson, W. B. Hutchinson, K. C. Ott, N. S. Hubbard, R. C. Dye, X. D. Wu, "Influence of Beam and Target Properties on the Excimer Laser Deposition of YBa.sub.2 Cu.sub.3 O.sub.7-x Thin Films", Los Alamos National Laboratory, Los Alamos, N. Mex. 87545, Materials Research Society Symp. Proc. Vol. 191, 1990, pp 205-209.
N. H. Cheung, Q. Y. Ying, J. P. Zheng, and H. S. Kwok, "Time-Resolved Resonant Absorbtion Study of 532-nm Laser-Generated Plumes Over YBa.sub.2 Cu.sub.3 O.sub.7 Targets", J. Appl. Phys. 69(9), 1 May 1991, American Institute of Physics, pp. 6349-6354.
T. Venkatesan, X. D. Wu, A. Inam, and J. B. Wachtman, "Observation of Two Distinct Components During Pulsed Laser Deposition of High T.sub.c Superconductor Films", Appl. Phys. Lett 52 (14), 4 April 1988, American Institute of Physics, pp 1193-1195.
A. Gupta, B. Braren, K. G. Casey, B. W. Hussey, and R. Kelly, "Direct Imaging of the Fragments Produced During Excimer Laser Ablation of YBa.sub.2 Cu.sub.3 O.sub.7-.delta. ", 1991.
G. Koren, A. Gupta, R. J. Baseman, M. I. Lutwyche, and R. B. Laibowitz, "Laser Wavelength Dependent Properties of YBa.sub.2 Cu.sub.3 O.sub.7-.delta. Thin Films Deposited by Laser Ablation", Appl. Phys. Lett 55 (23), 4 Dec. 1989, American Institute of Physics, pp 2450-2452.
A. Inam, and X. D. Wu, "Pulsed Laser Etching of High T.sub.c Superconductor Films", Appl. Phys. Lett 51 (14), 5 Oct. 1987, American Institute of Physics, pp 1112-1114.
E. G. Scott, S. T. Davey, M. A. G. Halliwell, and G. J. Davies, "Improvements to and Characterization of GaInAs Heterointerfaces Grown by Molecular-Beam Epitaxy", J. VAc.Sci. technol. B 6, March/April 1988, American Vacuum Society, pp. 603-605.
C. E. Otis, and R. W. Dreyfus, "Laser Ablation of YBa.sub.2 Cu.sub.3 O.sub.7-.delta. as Probed by Laer-Induced Fluorescence Spectroscopy", Physical Review Letters, 7 Oct. 1991, The American Physical Society, pp. 2102-2105.
T. Spalvins, "Lubrication with Sputtered MoS.sub.2 Films: Principles, Operation, and Limitations", ASM Journal of Materials Engineering and Performance, Vol. 1, No. 3, Jun., 1992, pp. 347-351 [cited as JMEPEG (1992)1:347-352], ASM International.RTM..
P. T. Murray, V. J. Dyhouse, L. Grazulis, and D. R. Thomas, "Dynamics of MoS.sub.2 Photoablation", Mat. Res. Symp. Proc. Vol. 201, 1991, Materials research Society, pp. 513-518.